Hey - learn the words for one, two, beer, please (bitter), and you're all set!
Ein Bier, bitte = a beer, please.
Noch ein Bier, bitte = another one
Although it can also be useful to eat:
Ein Bier und ein Wurst, bitte.
But I've always found it fascinating how most languages have such a large colloquial component. Before I went to Brazil, I went through a six month intensive language course (Defense Language Institute) in Portuguese. To show the depth of that school, they had six instructors, 2 from Portugal, 2 from the Azores, and 2 from Brazil (each is a different dialect). I was #1 in my class, and felt really confident when I finished it.
Then I went to Brazil. Got to my hotel and turned on the TV and understood no more than 10% of what I heard. It took probably close to a year before I really considered myself fluent (actually thinking in the language instead of translating on the fly).
By the time I left Brazil, three years later, I was routinely doing simultaneous interpretation for cabinet-level officials of both Brazil and the US, simply because there was nobody else available who could do that. I recognized that I had many hesitations and uncertainties, but they were all grateful and unaware of my weaknesses.
If I went back there today, I'm sure it would take me a couple of weeks to regain fluency, simply because my slang is so out of date.